import java.sql.Connection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class Test {
    public static void main(String[] args) {
        Set<Integer> set = new HashSet<>();
        set.add(1);
        set.add(1);
        set.add(2);
        set.add(3);
        System.out.println(set.contains(0));
        System.out.println(set.contains(1));
        System.out.println(set);
        set.clear();
        System.out.println(set);
    }

    public static void main1(String[] args) {
        Map<Integer,Integer> map = new HashMap<>();
        map.put(0,3);
      /*  System.out.println(map.get(0));
        map.remove(0);
        System.out.println(map.get(0));
        System.out.println(map.getOrDefault(2, 3));*/
        map.put(1,2);
        map.put(0,5);
        map.put(4,4);
        System.out.println(map.size());
        System.out.println(map.containsKey(4));
        System.out.println(map.containsKey(44));
        System.out.println(map.containsValue(2));
        System.out.println(map.containsValue(20));

      /*  Set<Map.Entry<Integer,Integer>> entries = map.entrySet();
        System.out.println(entries);*/
        /*Set<Integer> set = map.keySet();
        System.out.println(set);*/
    }
}
